Scanning systems are commonly used to form an image or pattern in a media or an imaging plane for displays printing, three-dimensional (3D) printing, metal engraving, and selective laser melting.
Referring to FIG. 1, scanning systems 100 generally include a spatial light modulator (SLM 102) to modulate light from a light source 104, a collimate lens 106 to form and direct multiple parallel beams from the SLM onto a scan mirror 108, and an imaging lens 110 to magnify and project modulated light from the scan mirror onto an imaging plane 112. The scan mirror 108 generally rotates around two axes to scan the modulated light over the imaging plane 112 to form an image or pattern.
One problem with conventional scanning systems, particularly those used to form an image or pattern on a two-dimensional (2D) imaging plane using multiple beams from a SLM 102, is that due to characteristics of imaging lenses used in these systems off-axis beams of multiple beams cannot scan parallel resulting in a distortion error that cannot be compensated for by increasing or controlling the speed of the scan mirror. That is a beam which has angle θ against an optical axis 114 of the imaging lens 110 settles at a position that is at a distance of fθ from a center of a swath or image 120 of the SLM 102 projected onto the imaging plane 112. This distance from the center of the image 120 increases as a function of the angle θ moving outward along the x-axis resulting in stretched or elongated, distorted image along the x-axis. Furthermore when the scan mirror is also rotated along a y-axis there is also distortion along the y-axis. Referring to FIG. 1, a dashed line 116 represents the desired or ideal location of a grid of images 120 of the SLM 102 projected and scanned along the x-axis on the imaging plane 112 while solid black lines 118 indicates a grid of the actual location of images of the SLM.
Accordingly, there is a need for a scanning system and a method for operating the same to compensate for distortion due to multi beam scanning optics.